The added value of SPECT/CT in the proper diagnosis of Heterotopic ossification by bone scintigraphy

Introduction: Heterotopic bone formation is a condition of abnormal osteogenesis in the non-skeletal tissue. It is a benign condition that can be difficult to detect accurately since it can mimic clinically & on imaging studies other conditions sometimes serious that require prompt intervention. The purpose of this study was to find the added value of SPECT-CT in the accurate scintigraphic detection of heterotopic ossification. Materials and Methods: One thousand, seven hundred and eighty reports on the PACS reporting system of patients underwent bone scintigraphy at the department of Nuclear Medicine were filtered for the term “heterotopic ossification or heterotopic bone formation” and “SPECT-CT”. Thirty-four patients (mean age, 54.2yrs; median age 58yrs; age range, 21-81 yrs.) fulfilled this criterion and were included. All patients had three phase bone scintigraphy in the same occasion of the SPECT-CT. The images were reviewed by two experienced nuclear medicine physicians blindly. The certainty of presence of extra-skeletal soft tissue ossification on the planar with SPECT were graded as definitely present, may be present or not present, in which case no uptake was seen or there is uptake which could not be viewed as HBF due to lack of separation from bony structures. Then these results were correlated with planar with SPECT-CT images.

Results: Based on the SPECT/CT findings, twenty-three (67.6%) patients were found to have heterotopic ossification and 11 (32.4%) did not have findings to confirm heterotopic ossification. Of the 23 positive patients on SPECT/CT, only 8 (34.8%) showed definitely present HBF on SPECT and 12 (52.2%) patients were categorized under may be present on SPECT only. Three (13%) patients were negative on the SPECT and actually showed evidence of heterotopic ossification on CT scan. Of the 11 patients that did not demonstrate definite evidence of heterotopic ossification on SPECT/CT, seven (63.6%) were negative on SPECT alone and 4 (36.4%) were under the unclear category “may be present” on SPECT.

Conclusions: Although the study population is small, our findings suggests that SPECT-CT is useful in the proper diagnosis of heterotopic bone formation.